System and Method for Marine Propulsion With Low Acoustic Noise

ABSTRACT

A propulsion system for a marine vessel in a body of water includes an water intake formed in the hull, a impeller disc rotatable about a vertical axis for raising water and increasing the momentum of water in a plenum chamber, and a plurality of control gates located around the periphery of the hull. The impeller disc has a large outer diameter and is formed to enable efficient rotation by an electric motor. One or more of the water intake, the plenum chamber, the impeller disc and the control gates is designed to reduce acoustic noise generated by the marine vessel, direct the acoustic noise to avoid broadband acoustic noise, increase efficiency of the propulsion system and provide additional safety to passengers on the marine vessel and marine life in the body of water.

BACKGROUND Field of the Disclosure

This disclosure relates generally to systems for propelling marinevessels relative to a body of water and, more particularly, to lowacoustic noise systems for propelling a marine vessel relative to a bodyof water.

Description of the Related Art

Marine propulsion refers to the mechanical means to impart motion to amarine vessel on or below the surface of water. Most commonly, some formof helical-screw propeller is rotated in the water by a motor or engineto generate thrust by increasing the momentum of the water. As areaction to the thrust, the marine vessel is propelled.

SUMMARY

Embodiments disclosed herein may be generally directed to a system forincreasing the momentum of water for the purpose of propelling a marinevessel and a system for controlling the emission of the water to controla direction in which the marine vessel is to be propelled.

Impeller discs may be more efficient than screw-type impeller discs byimparting radial momentum on the water as opposed to axial momentum.Embodiments of a vertically oriented impeller disc may be driven by anelectric motor mounted on top of a drive shaft extending along thevertical axis. The design of the propulsion system, including the designof individual components or the arrangement of components may allow forslow rotation of the vertically oriented impeller disc to reduce theacoustic noise generated in the water by ensuring the tip speed of theimpeller disc blades is maintained well below a cavitation speed, maydirect any acoustic noise away from the water intake or exit ports tominimize acoustic noise transmitted to the ambient water, and may ensureany acoustic noise exiting a marine vessel is directed to minimize therange over which the acoustic noise may affect marine animals.

Embodiments disclosed herein may be described as they pertain to a ferryboat used to transport passengers and cargo but may be useful in otherapplications with other types of marine vessels without departing inscope from the disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the invention and its features andadvantages, reference is now made to the following description, taken inconjunction with the accompanying drawings, in which:

FIG. 1 is a cutaway side view of an embodiment of marine vessel with apropulsion system configured for low noise propulsion of the marinevessel; and

FIG. 2 is a bottom view of the marine vessel of FIG. 1 , depicting aportion of one embodiment of a propulsion system with a water intakeoriented in a substantially downward vertical direction;

FIG. 3 is a cutaway bottom view of the marine vessel of FIG. 1 ,depicting a portion of one embodiment of a propulsion system with asingle vertically oriented centrifugal impeller disc configured for lownoise propulsion; and

FIG. 4 is a cutaway bottom view of a marine vessel, depicting a portionof one embodiment of a system configured with multiple verticallyoriented centrifugal impeller discs in a single plenum chamber.

DESCRIPTION OF PARTICULAR EMBODIMENT(S)

In the following description, details are set forth by way of example tofacilitate discussion of the disclosed subject matter. It should beapparent to a person of ordinary skill in the field, however, that thedisclosed embodiments are exemplary and not exhaustive of all possibleembodiments.

As used herein, a hyphenated form of a reference numeral refers to aspecific instance of an element and the un-hyphenated form of thereference numeral refers to the collective or generic element. Thus, forexample, control gate “132-1” refers to an instance of a control gate,which may be referred to collectively as control gates “132” and any oneof which may be referred to generically as control gate “132.”

For the purposes of this disclosure, a marine vessel may refer to aboat, a ship, a submarine or other form of transportation in a body ofwater.

The architecture and design of many marine vessels is based primarily onpropelling the marine vessel efficiently across large distances in abody of water. However, situations exist that marine vessel designs arechallenged to accommodate. In particular, several challenges of existingmarine vessel designs are associated with the use of a screw-typepropeller system oriented in a forward-aft plane.

A challenge with the design and operation of screw propellers is thegeneration of high levels of broadband acoustic noise. Acoustic noisemay be generated by the shape or design of a screw propeller and theoperation of a power source associated with the propeller. Ongoingscientific research indicates acoustic noise may adversely affect marineanimals and may be especially detrimental to certain species such aswhales. High levels of acoustic noise may travel over long distances.

As another challenge, the operation of screw propellers operating nearthe maximum rotational speed results in large losses in efficiency dueto friction forces on the propeller blades, adiabatic compression andconsequential heating of water near the propeller blades and acousticpressure waves radiating from the propeller.

As another challenge, in many marine vessel designs, a single propelleris mounted at a fixed angle in a forward-aft plane and a rudder ispositioned aft of the propeller to steer the marine vessel. By turningthe rudder, the direction of momentum of the water is changed, but witha loss of energy in the water. Some marine vessels, notably ferries,have multiple propellers mounted on rotatable vertical shafts thatenable directional changes of momentum of the water. The ability togenerate thrust at each propeller may be beneficial for delicatemaneuvering of a ferry near a dock, but these systems are complex.

As another challenge, in many marine vessel designs, the position of thepropeller is below most, if not all, other parts of the marine vesselfor reduced impedance of water being draw in into the propeller. Thislow position of the propeller exposes the propeller to the risk offouling by seaweed, rope or other debris present below the surface ofthe water, which may not be visible to a person on the marine vessel. Apropeller may be damaged by contact with a seabed, a reef or some othersurface at the bottom of the body of water.

As another challenge, in many marine vessel designs, exposed propellerspresent a safety hazard to marine life. There is evidence that marinemammals have been injured as they were swimming near the surface orsurfaced to breathe. Seaweed and other plant life may be entangled in apropeller and pulled out of the seabed.

To overcome these problems with marine vessels and prevent or mitigatenegative environmental effects associated with marine vessels,embodiments disclosed herein comprise a propulsion system configuredwith an impeller disc rotatable about a vertical axis to entrain waterin a direction independent of a speed or direction of travel of themarine vessel and accelerate the water in a radial direction, wherein aplurality of control gates arranged around the hull may be selectivelyopened and closed to propel the marine vessel. Embodiments may operateat higher efficiencies with reduced acoustic noise and a lower risk tomarine wildlife and the environment.

Turning to the drawings, FIG. 1 illustrates a side view depicting avertical section of marine vessel 100 from bow to stern. Marine vessel100 comprises an outer hull 110 configured to be at least partiallysubmerged in a body of water. In some embodiments, one or more decks 112and a bridge 114 may be located above the surface of the body of water.In some embodiments, marine vessel 100 may be configured with hull 110at least partially submerged in the body of water. FIG. 1 depicts oneembodiment of marine vessel 100 as a ferry boat with hull 110 configuredas a substantially straight surface from the bow to the stern. Hull 110may be configured with a flat bottom.

Marine vessel 100 comprises propulsion system 120 configured to be atleast partially submerged in the body of water. Propulsion system 120comprises water intake 122, impeller disc 124 rotatable about verticalaxis 126 and located in plenum chamber 128, electric motor 130 forrotating impeller disc 124 about vertical axis 126, a plurality ofcontrol gates 132 located near the periphery of hull 110, and controlsystem 150 for controlling rotational speed of impeller disc 124 andselectively opening and closing one or more control gates 132 directingwater through ports 137 in the hull to steer marine vessel 100. Marinevessel 100 may include batteries 148 for supplying electric power toelectric motor 130 for rotating drive shaft 147 about vertical axis 126or to one or more control gates 132.

Water intake 122 comprises one or more openings formed in hull 110 toallow a desired volumetric flow rate of water entering propulsion system120 but at a reduced velocity. Marine vessel 100 may be configured witha buoyancy to ensure marine vessel 100 is partially submerged in thebody of water with water intake 122 always below the surface of the bodyof water. In this configuration, water intake 122 may ensure avolumetric flow rate of water is naturally biased into propulsion system120. Reducing the velocity of water entering propulsion system 120 mayreduce the risk of debris, plants and animals from entering propulsionsystem 120 and may further reduce turbulence of water to reduce acousticnoise. In some embodiments, marine vessel 100 may be designed such thatwater intake 122 is always a minimum depth below the water surface,discussed in greater detail below.

Water intake 122 may be configured to reduce the effects that waterintake 122 has on marine vessel 100 moving in the body of water as wellas the effects that entraining water through water intake 122 has onmarine vessel 100 moving in the body of water. For example, water intake122 formed substantially parallel with respect to hull 110 may reducethe effects that a speed of marine vessel 100 has on a velocity of waterentering water intake 122 and may also reduce the possibility of debrisor animals entering water intake 122. In some embodiments, water intake122 may be formed in hull 110 and oriented in a direction relative to adirection of travel of marine vessel 100. For example, water intake 122may be formed in hull 110 and oriented substantially perpendicular to adirection of travel of marine vessel 100 to reduce the possibility ofdebris or animals entering water intake 122.

In some embodiments, water intake 122 oriented substantially downwardwith respect to hull 110 may direct any acoustic noise emitted bypropulsion system 120 downward (i.e., in an axial direction relative tovertical axis 126), which may reduce the distance that acoustic noisecan travel outward (i.e., in a radial direction relative to verticalaxis 126).

One or more of the location, size and shape of water intake 122 may beconfigured to improve stability of marine vessel 100 or provide forgreater safety or less acoustic noise. In some embodiments, water intake122 may be located at or near the lowest point of hull 110 and centrallylocated between the bow and stern to allow marine vessel 100 to approacha shore without a propeller contacting a bottom surface of the body ofwater. In some embodiments, water intake 122 may be formed near a keelof hull 110 and oriented in a downward direction, minimizing thepossibility that people or debris falling off a deck of marine vessel100 can be drawn into water intake 122. In some embodiments, waterintake 122 may be formed to minimize pressure variations associated withrotation of impeller disc 124.

Referring to FIGS. 1 and 2 , in some embodiments, water intake 122 maycomprise a plurality of inlet ports 123 formed in hull 110. The shape,size and orientation of inlet ports 123 may be selected to maximizesurface area of water inlet 122 to allow a desired volumetric flow rateof water into propulsion, reduce drag on marine vessel 100 due to waterflowing past water intake, reduce local pressure buildup associated withblade passing tone (BPT), minimize the size of marine life that canenter water intake 122 or some other factor. In some embodiments, waterintake 122 may be formed as a single opening and covered by a mesh orgrate to prevent marine life or debris from entering water intake 122.Advantageously, a mesh or grate covering water intake 122 may beconfigured to limit the size of items from entering water intake 122without affecting the volumetric flow rate of water entering waterintake.

Referring still to FIG. 1 , impeller disc 124 is positioned in plenumchamber 128 and rotatable about vertical axis 126. Impeller disc 124 maybe shaped to efficiently increase the momentum of water and direct thewater radially outward while minimizing or preventing pressure waves. Insome embodiments, impeller disc 124 may be formed with a large diametertop surface 134, a smaller diameter bottom surface 135 and an angledsurface 136 connected to top surface 134 and bottom surface 135, whereintop surface 134 may be considered as the base and angled surface 136 maybe considered as the side. Top surface 134 extends radially outward toan outer edge 138 with a large outer diameter. Top surface 134 may besubstantially flat or have a curvature formed to outer edge 138. Bottomsurface 135 may have a smaller outer diameter and be separated from topsurface 134 by a distance, wherein the distance corresponds to a heightof impeller disc 124.

Angled surface 136 may be straight or comprise a curvature between themost radially inward edge of angled surface 136 and the most radiallyoutward edge of angled surface 136. Referring to FIG. 1 , angled surface136 may have a generally straight cross-section profile, whereinimpeller disc 124 may resemble a frustro-conical shape. In otherembodiments (not shown), angled surface 136 may have a curvedcross-section profile. A curved cross-section profile may be based on asimple curve or a complex curve. For example, angled surface 136 mayhave a cross-section profile based on a tractrix. Other cross-sectionprofiles may be possible.

Angled surface 136 comprises a plurality of blades 140 shaped to movewater radially outward as impeller disc 124 rotates. As depicted in FIG.1 , blades 140 may be formed as substantially curved radially structuresof constant height or thickness. Referring to one or more of FIGS. 2-4 ,blades 140 may also be formed as curved structures with or withoutconstant height or thickness. For example, in some embodiments (notshown), blades 140 may be formed as curved structures based on theinvolute of a circle.

In some embodiments, impeller disc 124 may be formed to have a neutralor positive buoyancy. For example, impeller disc 124 may be formed withan enclosed hollow structure filled with air or some other fluid havinga lower density than water. In some embodiments, impeller disc 124 maybe configured as an enclosed hollow structure with an outer diametergreater than a portion of the width of hull 110. For example, impellerdisc 124 may be configured with outer edge 138 of top surface 134 havingan outer diameter greater than 25%, 50% or 60% of a width of hull 110,wherein a large hollow structure filled with air may provide buoyancywhen marine vessel 100 is at least partially submerged in water.

Impeller disc 124 may be formed with a structure such that power neededto move water through propulsion system 120 is substantially based onthe density of the water. For example, impeller disc 124 may comprise anenclosed hollow structure formed from a lightweight, high strengthmaterial, wherein the power needed to rotate impeller disc 124 alone ismuch less than the power needed to move water through propulsion system120.

Impeller disc 124 may have a base-height ratio selected for efficientlyraising water and increasing momentum of the water through propulsionsystem 120. In some embodiments, impeller disc 124 may be configuredwith a large diameter and a relatively small height. In theseconfigurations, electric motor 130 may be configured to generaterotational power with a high torque and a low rotational speed to raiseand accelerate water radially outward. Electric motor 130 mayefficiently rotate impeller disc 124 with reduced acoustic noise ascompared to diesel or other internal combustion engines. In someembodiments, impeller disc 124 formed as a hollow, lightweight structurewith a large base to height ratio may require less power to rotate,wherein batteries 148 may provide sufficient electric power to electricmotor 130 and control gates 132 to propel marine vessel 100.

Rotation of impeller disc 124 about vertical axis 126 may help stabilizemarine vessel 100. In some configurations, impeller disc 124 rotatingabout vertical axis 126 may function as a gyroscope, resisting forcesthat or reducing the amplitude of forces exerted by waves on hull 110.In some embodiments, the structure and material of impeller disc 124 maybe configured to function as a gyroscope. In some embodiments, thenumber, size and shape of blades 140 on impeller disc 124 may beconfigured to allow impeller disc 124 to function as a gyroscope evenwhen rotating at low rotational speeds. In some embodiments, thestructure and material of impeller disc 124 including the number, sizeand shape of blades 140 on impeller disc 124 may be configured to allowimpeller disc 124 to function as a gyroscope when impeller disc 124 isrotating at speeds less than 50 revolutions per minute. In otherembodiments, the structure and material of impeller disc 124 includingthe number, size and shape of blades 140 on impeller disc 124 may beconfigured to allow impeller disc 124 to function as a gyroscope whenimpeller disc 124 is rotating at speeds less than 30, 20 or 10revolutions per minute.

Plenum chamber 128 is configured to retain impeller disc 124 and providewater flow between water intake 122 and control gates 132, whereinrotation of impeller disc 124 in plenum chamber causes water flow fromwater intake 122 through plenum chamber 128 to control gates 132. Insome embodiments, plenum chamber 128 comprises lower wall 142 formedwith opening 131 in fluid communication with water intake 122. Asdepicted in FIG. 1 , in some embodiments, plenum chamber 128 comprisesbottom wall 129, lower wall 142 and upper wall. Lower wall extends frombottom wall 129 at a first diameter radially inward of water intake 122to a second diameter radially outward of outer edge 138 of impeller disc124 and has openings 131 corresponding to water intake 122. As impellerdisc 124 rotates, water is drawn in from water intake 122 throughopenings 131 and blades 140 accelerate the water in plenum chamber 128,wherein plenum chamber 128 directs the flow of water through hull 110 tocontrol gates 132. In some embodiments, plenum chamber 128 is formedwith upper wall 144 having a diameter larger than a diameter of outeredge 138 of impeller disc 124, wherein water pushed radially outward byimpeller disc 124 is circulated around plenum chamber 128 to theplurality of control gates 132.

The design of plenum chamber 128 may contribute to one or more of abuoyancy associated with propulsion system 120, an increased operatingefficiency of propulsion system 120, a reduction of acoustic noiseemitted by propulsion system 120 and the safety of marine life that mayinadvertently pass through propulsion system 120.

Plenum chamber 128 may be formed as a sealed chamber such that water canflow only through openings 131 and water intake 122 or any open controlgates 132. When all control gates 132 are closed, air may be containedwithin plenum chamber 128 to provide additional buoyancy. In someembodiments, the shape of plenum chamber 128 may contribute to thebuoyancy of hull 110. In some embodiments, plenum chamber 128 comprisesupper wall 144, bottom wall 129 and lower wall 142 formed to accommodatea shape of impeller disc 124 and allow for additional air in plenumchamber 128 above or radially outward if impeller disc 124. In thisconfiguration, plenum chamber 128 allows a greater volume of air at ahigher level and distributed over a wider area, which contributes to thebuoyancy and the stability of hull 110.

Positioning impeller disc 124 in plenum chamber 128 may prevent acousticnoise generated by blades 140 from being directly emitted into theambient water. Lower wall 142 may be formed with a shape and surface tofacilitate impeller disc 124 moving water upwards and accelerating thewater radially outwards. In some embodiments, lower wall 142 may beconfigured to reduce the amount of acoustic noise allowed to exitpropulsion system 120 directly into ambient water. For example, lowerwall 142 may be configured to deflect acoustic noise away from waterintake 122. In some embodiments, lower wall 142 may be formed from amaterial or coated with a material to deflect or absorb acoustic noise.

Lower wall 142 of plenum chamber 128 and angled surface 136 of impellerdisc 124 may be separated by a distance based on a desired volumetricflow of water through propulsion system 120. In some embodiments, lowerwall 142 and angled surface 136 may be separated by a minimum distancedetermined to minimize the risk of harming marine life that mayinadvertently enter water intake 122 and pass through propulsion system120. In some embodiments, lower wall 142 of plenum chamber 128 comprisesa shape complementary to the shape of angled surface 136 of impellerdisc 124, wherein a separation distance between lower wall 142 andangled surface 136 is substantially constant at all radii. In otherembodiments, lower wall 142 of plenum chamber 128 and angled surface 136of impeller disc 124 are shaped such that a separation distancedecreases radially outward.

As impeller disc 124 rotates in plenum chamber 128, blades 140 pushwater upward and accelerate the water radially outward, increasing themomentum of the water. Once water is raised in plenum chamber 128,plenum chamber 128 directs the water toward the plurality of controlgates 132 arranged around the periphery of hull 110.

Use of Control Gates to Generate Thrust

Control system 150 may open or close one or more control gates 132 togenerate thrust to propel and steer marine vessel 100. Referring toFIGS. 1 and 3 , one or more control gates 132 may be opened or closed byelectric motors or a hydraulic system to direct water exiting thecontrol gate 132 at an angle in a range 133 of angles. In someembodiments, each control gate 132 may be configured to rotate about alocal vertical axis over range 133 of angles. In some embodiments, range133 may be ninety degrees, wherein control gates 132 may be opened todirect water exiting the control gate 132 at any angle within range 133of ninety degrees. Control gates 132 configurable to direct water flowat an angle in a range 133 of angles may allow for fewer control gates132 but increased options for maneuvering marine vessel 100 in a body ofwater. For example, control system 150 may open or close only onecontrol gate 132 and rotate control gate 132 to steer marine vessel 100or may open or close a plurality of control gates 132 collectively butrotate individual control gates 132 to steer marine vessel 100. Controlsystem 150 may open or close one or more control gates 132 at one ormore angles to propel and steer marine vessel 100 or may operate aplurality of control gates 132 collectively to propel marine vessel 100in a forward direction, an aft direction, a port direction or astarboard direction, to turn the marine vessel 100 toward port orstarboard, to rotate marine vessel about a point or to stop marinevessel 100. As depicted in FIG. 1 , at least one control gate 132located near the periphery of hull 110 at the stern end of marine vessel100 is open and at least one control gate 132 located near the peripheryof hull 110 at the bow end of marine vessel 100 is closed. Water flowthat is directed out of the at least one stern control gate 132generates thrust. As a reaction, marine vessel 100 may be propelled inthe opposite direction. Referring to FIG. 3 , for example, control gates132-1 and 132-4 may be open and control gates 132-2 and 132-3 may beclosed such that thrust is generated in an aft direction to propelmarine vessel 100 in a forward direction. In some embodiments, eachcontrol gate 132 comprises an outer surface that reduces drag on hull110 when control gate 132 is closed.

In these configurations, controlling a direction of travel of marinevessel 100 does not rely on drag forces applied to a rudder. Instead,controlling a direction of travel may involve control system 140 openinga first set of control gates 132 and closing a second set of controlgates 132. In these configurations, embodiments avoid inefficienciessuch as directional propellers imparting drag on marine vessel 100.

Multiple Impeller Discs

In some environments or marine vessel applications, a hull 110 may beconfigured such that a single impeller disc 124 may provide insufficientincrease in water momentum for marine vessel 100. For example, hull 110may be formed with a large length to width ratio such that the diameterof impeller disc 124 is limited. Referring to FIG. 4 , in someembodiments, a marine vessel 400 may operate with two impeller discs 124in a single plenum chamber 128. In some embodiments (not shown) multipleimpeller discs 124 may be positioned relative to a common water intakein hull 110. The water intake may be elongated, such as an oval orrectangular design. In other embodiments (not shown) each impeller disc124 may be positioned relative to a respective water intake such aswater intake 122 and each water intake 122 may be in fluid communicationwith plenum chamber 128. Multiple impeller discs 124 may counterrotateas depicted in FIG. 4 or may rotate in the same angular direction.

The above disclosed subject matter is to be considered illustrative, andnot restrictive, and the appended claims are intended to cover all suchmodifications, enhancements, and other embodiments which fall within thetrue spirit and scope of the disclosure. Thus, to the maximum extentallowed by law, the scope of the disclosure is to be determined by thebroadest permissible interpretation of the following claims and theirequivalents, and shall not be restricted or limited by the foregoingdetailed description.

What is claimed is:
 1. A propulsion system for a marine vessel, thepropulsion system comprising: a water intake formed in a hull, the waterintake open to ambient water; an impeller disc rotatable about avertical axis, the impeller disc comprising: a top surface orthogonal tothe vertical axis, the top surface extending radially outward to a topsurface outer edge; and a bottom surface separated from the top surfaceby a distance and extending radially outward to a bottom surface outeredge; and an angled surface extending between the bottom surface outeredge to the top surface outer edge, the angle surface comprising aplurality of blades; a plenum chamber for containing the impeller disc,the plenum chamber comprising an upper wall extending radially outwardof the top surface outer edge; a bottom wall having a bottom wall outerdiameter radially inward of the water intake; and a lower wall extendingfrom the bottom wall radially inward of the water intake to the upperwall to the upper wall radially outward of the water intake, the lowerwall having an opening in fluid communication with the water intake; aplurality of control gates in fluid communication with the plenumchamber and located near the periphery of the hull; and a control systemconfigured to: rotate the impeller disc to cause water flow from thewater intake to the plurality of control gates; and open one or more ofthe plurality of control gates, wherein water exiting the one or more ofthe plurality of control gates flows into the ambient water to generatethrust.
 2. The propulsion system of claim 1, wherein the impeller disccomprises a hollow structure.
 3. The propulsion system of claim 1,wherein a separation distance between the angled surface of the impellerdisc and the lower wall of the plenum chamber is substantially constantat all radii.
 4. The propulsion system of claim 1, wherein a separationdistance between the angled surface of the impeller disc and the lowerwall of the plenum chamber decreases radially outward.
 5. The propulsionsystem of claim 1, wherein one or more of the plenum chamber and theimpeller disc is configured for neutral buoyancy in water.
 6. Thepropulsion system of claim 1, wherein one or more of the plenum chamberand the impeller disc is configured for positive buoyancy in water. 7.The propulsion system of claim 1, wherein one or more of the pluralityof control gates is at least partially above a surface of the ambientwater.
 8. The propulsion system of claim 1, wherein one or more of theplenum chamber and the impeller disc is proportioned and configured todeflect acoustic noise away from the water intake.
 9. The propulsionsystem of claim 1, wherein the water intake comprises a plurality ofnarrow slots oriented relative to a length of the vessel.
 10. Thepropulsion system of claim 1, wherein each control gate is configurableto direct water exiting the control gate at an angle selected from arange of ninety degrees.
 11. A marine vessel comprising: a hullcomprising an outer surface; a water intake formed in the outer surfaceof the hull in a substantially vertically downward direction; animpeller disc rotatable about a vertical axis, the impeller disccomprising: a top surface orthogonal to the vertical axis, the topsurface extending radially outward to a top surface outer edge; and abottom surface separated from the top surface by a distance andextending radially outward to a bottom surface outer edge; and an angledsurface extending between the bottom surface outer edge to the topsurface outer edge, the angle surface comprising a plurality of blades;a plenum chamber for containing the impeller disc, the plenum chambercomprising an upper wall extending radially outward of the top surfaceouter edge; a bottom wall having a bottom wall outer diameter radiallyinward of the water intake; and a lower wall extending from the bottomwall radially inward of the water intake to the upper wall to the upperwall radially outward of the water intake, the lower wall having anopening in fluid communication with the water intake; a plurality ofcontrol gates in fluid communication with the plenum chamber and locatednear the periphery of the hull; and a control system configured to:rotate the impeller disc to cause water flow from the water intake tothe plurality of control gates; and open one or more of the plurality ofcontrol gates, wherein water exiting the one or more of the plurality ofcontrol gates flows into the ambient water to generate thrust.
 12. Themarine vessel of claim 11, comprising: an electric motor coupled to theimpeller disc; and the electric motor is configured to rotate theimpeller disc at low rotational speed.
 13. The marine vessel of claim11, wherein a diameter of an outer edge of the impeller disc is greaterthan 25% of a width of the marine vessel.
 14. The marine vessel of claim11, wherein a diameter of the upper wall of the plenum chamber isgreater than 25% of a width of the marine vessel.
 15. The marine vesselof claim 11, wherein: the hull comprises a flat bottom; and the waterintake is configured to open substantially in a downward direction.